Lituites tenuicaulis Remelé, 1890

Aubrechtová, Martina & Korn, Dieter, 2022, Taxonomy and ontogeny of the Lituitida (Cephalopoda) from Orthoceratite Limestone erratics (Middle Ordovician), European Journal of Taxonomy 799 (1), pp. 1-108 : 72-75

Lituites tenuicaulis Remelé, 1890

Figs 50–53 , Tables 9–11

Lituites tenuicaulis Remelé, 1890 : pl. 3 fig. 2.

Lituites procerus – Foerste 1932: 166, text-fig. 7.

Lituites tenuicaulis – Balashov 1953: 231, pl. 14 fig. 1. — Aubrechtová & Meidla 2020: 278.

Diagnosis

Species of the genus Lituites with the coiled conch 30 mm in diameter; 2–3 tightly coiled whorls, only the mid-part of the last whorl sometimes detached; whorl expansion rate 1.90–2.30. Uncoiled part straight in shape or slightly curved, expansion angle 2–3°. Shell surface in coiled part with fine growth lines and sharp lirae, sometimes with narrow annuli; in the backcoiled part with lirae and low annuli (after Balashov 1953; emended).

Type material

Lectotype GERMANY • Brandenburg, Oderberg; Ordovician (late Lasnamägi Regional Stage, late Darriwilian), Upper Grey Orthoceratite Limestone; Kgl. Forstakademie Eberswalde Coll.; designated by Balashov (1953); illustrated by Remelé (1890: pl. 3 fig. 2), re-illustrated here in Fig. 50A ; MB.C.5389 .

Additional material

GERMANY • 1 spec.; Brandenburg, Eberswalde; Ordovician, Upper Grey Orthoceratite Limestone; Remelé 1884 Coll.; MB.C.11651 • 2 specs; Brandenburg, Niederfinow; Ordovician, Upper Grey Orthoceratite Limestone; Neben and Krueger Coll.; MB.C.30548 , MB.C.30549 • 1 spec.; Brandenburg, Ringenwalde; Ordovician, Upper Grey Orthoceratite Limestone; Neben and Krueger Coll.; MB.C.30550 .

POLAND • 1 spec.; West Pomerania, Island of Chrząszczewska (former Gristow); Ordovician, Upper Grey Orthoceratite Limestone; Müchner Coll.; MB.C.30551 .

Description

Lectotype MB.C.5389 ( Fig. 50A ) consists of the coiled part (dm = 28 mm; 1.5 tightly coiled volutions slightly detached in the last half volution) and a part of the backcoiled part (length = 50 mm; wh = 12.4 mm; EA = 2.7°). The whorl profile is compressed (WWI = 0.88). The shell wall is preserved only in the last portion of the coiled part; there the ornament consists of sharp lirae (less than 1 mm apart) and fine growth lines between them. The backcoiled part of the specimen additionally shows imprints of annuli of about 1 mm apart. The chamber length increases during ontogeny from CLR ~ 0.36 to ~ 0.52 ( Fig. 52A–B ). The siphuncle is visible at the last preserved septum, where it has a relative diameter of 0.18 and a position of 0.32.

A more completely preserved ornament is seen in the specimen MB.C.30551 ( Fig. 50B ). In this specimen, the coiled part has lirae and narrow annuli, which grade into flat annuli after uncoiling (3–4 mm apart). The annuli of the backcoiled part have coarse lirae in between them (0.3–0.5 mm apart). The ventral sinus of ornament elements is deep and rounded ( Fig. 53 ). In the coiled part, the ornament elements are laterally straight, while in the backcoiled part, they have a shallow lateral sinus.

Specimen MB.C.30548 has a well-preserved coiled part ( Fig. 51 ), which consists of nearly two tightly coiled volutions that are slightly detached in the last half volution. By contrast to the lectotype, the chamber length in MB.C.30548 decreases during ontogeny from CLR ~ 0.40 to ~ 0.25 ( Fig. 52C–D ).

Remarks

Lituites tenuicaulis is distinguished from other species of Lituites by a comparatively large, tightly or nearly tightly coiled conch, an almost straight, slowly expanding backcoiled part and an ornament with lirae in the coiled part, low and wide annuli in the backcoiled part. In these characters, the species is similar to Trilacinoceras discors but that species has smaller, more slender and openly coiled conch.

Geographic and stratigraphic occurrence

Estonia (in situ), northern Germany and northern Poland (in erratics within Pleistocene gravels); late Darriwilian, Middle Ordovician.

Figures

Fig. 50. Lituites tenuicaulis Remelé, 1890 from the Upper Grey Orthoceratite Limestone. A. Lectotype MB.C.5389 (Kgl. Forstakademie Eberswalde Coll.) from Oderberg (Brandenburg); photograph and reproduction of the illustration by Remelé (1890: pl. 3 fig. 2). B. Specimen MB.C.30551 (Münchner Coll.) from Island of Chrząszczewska (former Gristow; West Pomerania, Poland). Scale bar units = 1 mm.

Fig. 51. Lituites tenuicaulis Remelé, 1890. A. Outline of coiled conch part of specimen MB.C.30548. B–E. Conch proportions and coiling rates of specimen MB.C.30548. Scale bar units = 1 mm.

Fig. 52. Septum distances in Lituites tenuicaulis Remelé, 1890 from the Upper Grey Orthoceratite Limestone. A, C = empirical data points; B, D = three data points averaged. A–B. Lectotype MB.C.5389 (Kgl. Forstakademie Eberswalde Coll.) from Oderberg (Brandenburg). C–D. Specimen MB.C.30548 (Neben & Krueger Coll.) from Niederfinow (Brandenburg).

Fig. 53. Lituites tenuicaulis Remelé, 1890 from the Upper Grey Orthoceratite Limestone; lirae in specimen MB.C.30551 (Münchner Coll.) from Island of Chrząszczewska (former Gristow; West Pomerania, Poland), at wh = 12.5 mm. Scale bar units = 1 mm.